A common receipt, issued by a printer installed at the cash desk of a commercial concern, is normally obtained from a continuous ribbon, or from a strip coming from a roll housed inside the printer, and generally bears a graphic representation in a first area, which is repeated identically on each receipt, such as a symbol or a logo or a wording indicative of and suitable for identifying the concern issuing the receipt, and a range of data in a second area, data that can obviously vary from receipt to receipt and, on account of this, also called variable data, such as the list of items purchased and the relative amount, in respect of the specific operation carried out by the user in the concern associated with the cash desk.
It is very important that the steps connected with printing and issuing a receipt are performed extremely rapidly in order to reduce waiting times of the users, and accordingly reduce the risk of queues forming at the cash desks, especially in those places, such as supermarkets, where user traffic is particularly high.
Unfortunately this requirement to print receipts as quickly as possible is often in conflict with the fact that printing of the logo or symbol identifying the commercial concern may require considerable printing times, times that are added to those for printing the variable data, especially when the logo is a complex one, is of a certain size and/or is in colour.
In these cases in fact, the complete printing of a receipt, i.e. of the constant data such as the fixed, preestablished logo identifying the commercial concern, and of the variable data indicative of the operation carried out, may involve a significant waiting time, that impacts considerably on the total waiting times of a user at the cash desk, possible result of which is the undesirable generation of queues of users at this cash desk.
Numerous are the types of printing devices currently used in commerce, provided for issuing receipts, and which work by printing data on a continuous ribbon of paper coming from a roll on which the ribbon is wound, and subsequently cutting the printed ribbon in order to form a receipt.
These devices adopt various technologies for printing the receipts, in particular the technology called thermal paper printing, for simplicity's sake also called thermal printing technology for short, and the ink jet technology, technologies which may undoubtedly be considered as the most widespread and used on the market.
In the former case, printing is performed by a dot matrix type printhead, usually not having transversal movements with respect to the paper ribbon and having a width roughly corresponding to the width of the line of print to be printed on the ribbon, in which the printhead is arranged for sliding in contact with a special or surface-treated paper, also called thermal paper. During printing, while the paper advances in front of the head, the dots of the latter are selectively heated to transmit the heat generated to the thermal paper, which accordingly blackens so as to generate the printed characters and/or symbols.
In the second case, printing is performed by a printhead, again dot-matrix type, generally provided with an alternating motion in front of the paper ribbon coming from the roll, in which the printhead comprises numerous nozzles suitable for selectively emitting, during the alternating motion, droplets of black or colour ink on the paper, usually plain type, i.e. not treated, to generate on the latter the characters and/or printed symbols.
In a variant of the thermal printing technology, much used for printing receipts and also called ink transfer thermal technology, printing can be performed on plain paper, i.e. not thermal and not treated; here a dot matrix printhead, structurally similar to the one mentioned above, is used for printing on special thermal paper, and a ribbon on which a thin layer of solid ink has been deposited is inserted between the printhead and the normal paper.
In practice, the dots of the head are heated selectively in order to heat dot-like areas of the ribbon which, in this way, in correspondence with the heated areas, causes the ink to melt and be released on the paper, so that the characters and/or printed symbols are generated on the latter.
On the subject of the two printing technologies recalled above, the thermal printing technology, including that on special thermal paper and that on plain or normal paper in the ink transfer variant, has the important advantage of being quite economical, at least for printing in black and white, and has the characteristic that it allows numerous lines to be printed on a receipt at a high printing speed, and also produces a print of very sharp and precise definition, as is required in particular in printing special symbols such as the bar codes widely used on receipts.
Conversely, the thermal printing technology is slow and sometimes not economically convenient for colour printing, in this case requiring the use of very high cost accessories, such as special papers and multicolour type thermal transfer ribbons; in addition, it requires special mechanisms and circuits for management of these accessories, and these cause the cost of the printer to soar.
On the other hand, the ink jet printing technology has the advantage of being competitive, with respect to the thermal technology, for colour printing, on account of offering a higher print speed, of being able to produce colour printing on a printer built substantially like a standard ink jet printer for black and white printing, and on account of the fact that it uses accessories, such as a specific printhead containing various coloured inks, having a structure and therefore a cost not unlike those envisaged for black and white printing.
Against this, an ink jet printhead, due to its alternating motion with respect to the paper ribbon to cover the various lines of a receipt, may imply a much greater time to print these lines than a thermal printhead, at least for black and white printing.
These known devices or printers do not, however, appear to solve in full the problem of printing a receipt in a substantially limited time, and thus satisfy all the operating requirements and market requirements, so that there is still considerable space and opportunity for further improvement.
In particular, it has been seen that the time to print the logo, whether at the top or the bottom of the receipt, significantly impacts upon the time the user has to wait at the cash desk, before receiving the fully printed receipt.